The World Will Exceed Its "Carbon Budget" in 12 Years, According to UN Report

Scientists have spent considerable time calculating the amount of carbon dioxide the world can emit while limiting warming to internationally agreed upon temperature goals – well below 2°C (3.6°F), with efforts to limit warming further to 1.5°C (2.7°F). This amount is our “carbon budget.”

The Intergovernmental Panel on Climate Change’s (IPCC) new report takes stock of the most recent literature on the carbon budget. The bottom line? We’re on track to blow through it over the next decade.

What is the remaining carbon budget if we’re to limit warming to 1.5°C?

To have a medium chance of limiting warming to 1.5°C, the world can emit 770 gigatonnes of carbon dioxide (GtCO2). To have a likely chance (67 percent), the remaining budget drops to 570 GtCO2.

Even if countries fulfill their current unconditional emissions-reduction pledges, we’re on track to blow through the entirety of the remaining carbon budget for a likely chance of limiting warming to 1.5° by 2030.

Even in the overly optimistic scenario in which current levels of carbon dioxide emissions are held constant, we would still exhaust the budget in 2030 (for a likely chance of limiting warming to 1.5°C). This clearly illustrates the need to peak global emissions before 2030 to have a better chance of avoiding the worst climate impacts.

To have likely chance of keeping warming to 1.5°C over the longer term, the world will need to reach net-zero emissions within 25 years.

What about for 2°C?

The remaining budget is considerably higher to limit warming to 2°C: 1690 GtCO2 for a 50 percent chance, or 1320 GtCO2 for a 67 percent chance.

In the overly optimistic scenario of current levels of carbon dioxide emissions being held constant, this budget would be exhausted by 2049 (for a likely chance of limiting warming to 2°C).

What is the role of carbon removal in reaching 1.5°C?

The report also finds that if we exceed the carbon budget, meeting the 1.5 ˚C goal will require carbon removal, a process where we’re actually taking carbon from the atmosphere and storing it. Almost all of the models used in the IPCC report rely on carbon removal to some extent.

There are a number of different ways to remove carbon, such as bioenergy with carbon capture and storage (BECCS), afforestation and direct air capture and storage (DACS). Importantly, models where temperature rise exceeds 1.5˚C before dropping back down rely much more heavily on carbon removal.

Deploying carbon at the scale that climate models assume is untested. Given the risks and uncertainties related to various carbon removal approaches, scaling would have to be pursued in a safe and prudent manner. If the speed and scale of deployment is limited, this would leave a lot of questions on how much we can rely on this strategy to meet the 1.5 degree goal, especially for those pathways that overshoot 1.5˚C.

Why is the remaining carbon budget larger than estimates from the IPCC’s Fifth Assessment Report?

A significant body of literature has emerged since the Fifth Assessment Report was released in 2014, and, as a result, the IPCC’s report on 1.5°C includes a larger carbon budget. More recent estimates have adjusted for the difference between recent observations of historical warming and cumulative emissions with those used in the IPCC’s Fifth Assessment Report’s Earth system modeling. (Others have notedthat there is no such discrepancy once comparisons are corrected for various biases.)

More recent efforts have tried to incorporate the latest observations of past emissions and warming. After doing so, these estimates have looked at the difference between current warming to date compared with 1.5°C and then calculated how much more we could emit accordingly.

Although the difference with the older modeling results is relatively small, given the very small budgets associated with 1.5°C, this can lead to significant differences in the calculated budget. Accordingly, the budgets associated with 1.5°C are particularly sensitive to different assumptions and uncertainties.

Why are the key differences and uncertainties regarding calculations of the budget?

Scientists’ estimations of the remaining carbon budget vary. Key differences include the choice of model used, methodological choices, assumptions regarding historical emissions and the warming realized to date, and the extent of overshooting temperature targets, among other factors. Also, some carbon budgets are CO2-only, while others include all greenhouse gases and aerosols. Budgets that don’t take into account non-CO2 gases overestimate the carbon budget.

There are many uncertainties regarding the calculation of the remaining carbon budget, including the Earth’s climate response to carbon emissions, the role of non-CO2 emissions, climate feedbacks and more. In fact, the IPCC states that uncertainties in the climate budget contribute ±400 GtCO2, and uncertainties regarding the level of historic warming contributes ±250 GtCO2 to the budget. And as a result, the timing of bringing carbon dioxide emissions down to net-zero can vary by ±15–20 years.

One important uncertainty is with regard to climate feedbacks, or a cascade of impacts that can result in greater warming. For example, if the remaining budget was stretched out to 2100, it would be roughly 100 GtCO2 lower because of the potential release of methane from wetlands and thawing permafrost.

Staying Within the Carbon Budget

We have already burned through a large portion of our carbon budget, and recently at an alarming rate. It is clear from the report that if emissions continue unabated, even with countries’ current climate commitments being fully implemented, we blow through the budget in just about a decade’s time for a likely chance of limiting warming to 1.5°C. Doing so would expose the world to even more severe heat waves, sea level rise, extreme rainfall and other climate impacts. The IPCC makes it clear that we can no longer emit at our carbon-intensive rate if we are to avoid the worst climate impacts. We must instead rapidly turn around our emissions trajectory.

12:09AFP: Protesters angry over high fuel prices blocked access to fuel depots and stopped traffic on major roads after the government refused to back down on fuel taxes after a weekend of demonstrations across France

09:24Bloomberg: Saudi Arabian stocks declined the most in a month after the U.S. sanctioned 17 officials over the death of Jamal Khashoggi

09:17CNN: President Trump says he declined to listen to a recording that captured part of the killing of journalist Jamal Khashoggi, calling it "a suffering tape" and "terrible"

09:13The Sun: Opponents of British Prime Minister Theresa May are six letters short of the threshold to trigger a no confidence vote

09:10AP: Disaster coordination authorities have asked eight communities in Guatemala to evacuate and go to safe areas after an increased eruption of the Volcano of Fire

09:07AP: The search for remains of victims of the devastating Northern California wildfire has taken on new urgency as rain in the forecast could complicate those efforts while also bringing relief to firefighters on the front lines

08:24Reuters: Chinese city urges those 'poisoned by extremism', who follow conservative Islam to confess crimes

08:24Interfax: Kremlin says Putin told Pence Russia did not meddle in U.S. election

08:23AP: French President Emmanuel Macron and German Chancellor Angela Merkel consulted Sunday on migration, fixing the euro currency, Europe’s defense, taxing digital companies and other issues as the two leaders looked to preserve their influence abroad

08:13Al-Arabiya: Two Yemeni fishermen were killed on Sunday evening by a sea mine laid by the Houthis in a coast of Hodeidah port city, west of the country

08:12Al-Arabiya: Ten Iranian parties and political forces have reportedly agreed to form a coalition to set plans in motion that aim at “overthrowing the regime in Tehran”, according to sources familiar with the groups

07:50Al-Arabiya: Jim Hanson, the president of the Security Studies Group, told Fox News that the leaks of classified information that the Washington Post and other news outlets are relying on regarding the Khashoggi case are “not something that should be the final say

07:37Reuters: British Prime Minister Theresa May said that toppling her would risk delaying Brexit and she would not let talk of a leadership challenge distract her from a critical week of negotiations with Brussels

07:35France's Macron: Germany, France must break taboos to advance on European reforms

07:34Reuters: Syrian army advances against Islamic State in southeastern desert

07:27Yemen’s Houthi movement said it was halting drone and missile attacks on Saudi Arabia, the UAE and their Yemeni allies, responding to a demand from the UN

12:46Austrian minister: Ministers from 27 non-British EU members agree not to reopen talks on draft Brexit deal ahead of its signing this weekend

12:29AFP: Ministers from 27 EU member states are meeting in Brussels to thrash out a plan for close ties with post-Brexit Britain in the last week before they gather to sign their divorce papers

12:09AFP: Protesters angry over high fuel prices blocked access to fuel depots and stopped traffic on major roads after the government refused to back down on fuel taxes after a weekend of demonstrations across France

12:00AFP: The toll from the deadliest and most destructive wildfire in California's history has risen to 77, the sheriff's office has said, after a vigil to honor the victims

09:13The Sun: Opponents of British Prime Minister Theresa May are six letters short of the threshold to trigger a no confidence vote

09:10AP: Disaster coordination authorities have asked eight communities in Guatemala to evacuate and go to safe areas after an increased eruption of the Volcano of Fire

09:07AP: The search for remains of victims of the devastating Northern California wildfire has taken on new urgency as rain in the forecast could complicate those efforts while also bringing relief to firefighters on the front lines

08:24Reuters: Chinese city urges those 'poisoned by extremism', who follow conservative Islam to confess crimes

08:24Interfax: Kremlin says Putin told Pence Russia did not meddle in U.S. election

08:23AP: French President Emmanuel Macron and German Chancellor Angela Merkel consulted Sunday on migration, fixing the euro currency, Europe’s defense, taxing digital companies and other issues as the two leaders looked to preserve their influence abroad

07:37Reuters: British Prime Minister Theresa May said that toppling her would risk delaying Brexit and she would not let talk of a leadership challenge distract her from a critical week of negotiations with Brussels

07:35France's Macron: Germany, France must break taboos to advance on European reforms